Various methods of relaxation and of biofeedback have been used to teach control of blood pressure. Questions have been raised as to the confounding of the variables (relaxation and biofeedback), the need for controlled group outcome studies, the infrequent use of patients as subjects, and the need for adequate baseline and follow-up data. Does biofeedback add anything to simple relaxation? If it does, should biofeedback be taught directly in the mode of the stress response (e.g. blood pressure)? Or should some form of relaxation be used to facilitate teaching biofeedback in the mode of the stress response? Can tonic (inter-session, long term) effects rather than merely phasic (intra-session) effects be demonstrated? What are the hormonal correlates of blood pressure reduction? The present study addresses itself to the above questions in an additive design. It uses a behavioral criterion during an elastic baseline period, thus handling the problem of noncompliance. Follow-up continues for at least 6 mo.-1 year. Hypotheses to be tested are: 1) EMG-assisted relaxation is superior to general relaxation without biofeedback. 2) Direct blood pressure biofeedback is superior to a low-arousal condition, i.e., relaxation, whether EMG-assisted or not. 3) Simple relaxation prior to direct blood pressure biofeedback facilitates the control of hypertension. 4) Tonic reductions in blood pressure as a result of relaxation and/or biofeedback training are correlated with changes in plasma renin activity, plasma cortisol, plasma aldosterone, and plasma norepinephrine.